We are continuing a study of the transition from early to late lambda DNA replication. Experiments have been completed which show that the first round of replication terminates wherever growing points happen to collide. (There is no eveidence of a unique termination point). An investigation of second and later rounds of replication is in progress. We are also trying to isolate replicative intermediates in which the replicative machinery is still intact. Recombination: Junctions, suggestive of recombination, have been observed and investigated in intracellular lambda DNA. We wish to determine if in fact they do represent recombinational intermediates. Minor Projects: Comparison of physical and genetic maps of P2 have been completed and homology between P2 and 186 determined. Various composite and chimeric molecules have been characterized by denaturation mapping. The order in which Mu DNA is packaged has been investigated. Bibliographic references: Record, M.T., C.P. Woodbury and R.B. Inman> (1975). Characterization of rod-like DNA fragments. biopolymers 14, 393. Tanaka, T., B. Weisblum, M. Schnos and R. B. Inman. (1975). Construction and characterization of a chemeric plasmid composed of DNA from E. coli and Drosophila melanogaster. Biochemistry 14, 2064.